CD274 and breast cancer: Also, PD-L1 acts as a predictive biomarker for response to cytokine-induced killer cell-based immunotherapy in breast cancer patients, and targeting PD-L1 displayed an anti-cancer effect in the treatment of breast cancer (Dirix et al., 2018; Zhou et al., 2019) Thus, it is interesting to find agents inhibiting PD-L1 expression.